On the effect of sodium dodecyl sulfate on the structure of beta-galactosidase from Escherichia coli. A fluorescence study.

An understanding of the structure-function relationship of proteins under different chemical-physical conditions is of fundamental importance for an understanding of their structure and function in cells. In this paper we report the effects of sodium dodecyl sulfate and temperature on the structure of beta-galactosidase from Escherichia coli, as monitored by fluorescence spectroscopy. The structure of the protein was studied in the temperature range of 10-60 degrees C in the absence and presence of sodium dodecyl sulfate by frequency-domain measurement of the intrinsic fluorescence intensity and anisotropy decays. The time-resolved fluorescence data in the absence of SDS indicated that at 10 degrees C the tryptophanyl emission decays were well described by a three exponential decays model, and that the temperature increase resulted in shortening of the long-lived component with little change in the short- and middle-lived components. The addition of SDS to the protein solution also affected the long-lived component. The effects of the detergent and temperature on the enzyme structure were also investigated by means of quenching experiments and anisotropy decays. The obtained results showed that the presence of SDS confers more flexibility to the protein structure, and suggest a strict relation between enzyme activity and protein flexibility.

A thermophilic apoglucose dehydrogenase as nonconsuming glucose sensor.

Blood glucose is a clinically important analytes for diabetic health care. In this preliminary report we describe a protein biosensor for d-glucose based on a thermostable glucose dehydrogenase. The glucose dehydrogenase was noncovalently labeled with 8-anilino-1-naphthalene sulfonic acid (ANS). The ANS-labeled enzyme displayed an approximate 25% decrease in emission intensity upon binding glucose. This decrease can be used to measure the glucose concentration. Our results suggest that enzymes which use glucose as their substrate can be used as reversible and nonconsuming glucose sensors in the absence of required cofactors. Moreover, the possibility of using inactive apoenzymes for a reversible sensor greatly expands the range of proteins which can be used as sensors, not only for glucose, but for a wide variety of biochemically relevant analytes.

Experimental allergic encephalomyelitis in guinea pig: variability of response to intradermal emulsion injection.

Different forms of experimental allergic encephalomyelitis were obtained in 4 groups of guinea pigs: 7 adult Hartley guinea pigs (Group I), 12 adults of the same strain (Group II), 6 juvenile strain 2 guinea pigs (Group III) and 6 juvenile strain 13 animals (Group IV), by the injection of emulsions. Groups I and II received emulsions containing 250 mg and 500 mg respectively of fresh isologous spinal cord tissue, complete Freund adjuvant (CFA) and saline solution while Groups III and IV received an emulsion containing 120 mg of isologous spinal cord, CFA, saline solution and 15 mg of Mycobacterium tuberculosis. The increased antigen load induced a disease with delayed onset and prolonged progressive course (C-P-EAE) in Groups I and II, although 8 animals showed no symptoms of illness. The findings in C-P-EAE were large demyelinated plaques, perivenous fibrosis and large areas of infiltration. Demyelinated areas occurred within the spinal cord white matter only in two asymptomatic animals. C-P-EAE was obtained in 4 of the Strain 2 animals. In conclusion, the increased antigen load induced a range of lesions in Hartley guinea pigs, although not all animals were affected. C-P-EAE was induced also in strains of guinea pig other than the Heartley strain. These different reactions may have been the outcome of partial or complete inactivation of the cell-mediated response to the inoculated antigens.